This invention relates to a high voltage discharge lamp apparatus for activating a high voltage discharge lamp, and more particularly relates to a discharge lamp apparatus for use as a headlight of a vehicle.
Various lighting apparatuses for vehicles using a high voltage discharge lamp (ballast) are proposed in, for instance, JP-U-6-86203, JP-A-8-321389, JP-A-9-180888 and EP 0955793 A2 (U.S. patent application Ser. No. 09/304840 and now U.S. Pat. No. 6,232,728 issued May 15, 2001).
The discharge lamp apparatus is mounted in a limited space such as the outside (side face) of a housing of a headlight of a vehicle. In the discharge lamp apparatus, a DC power of a vehicle-mounted battery is boosted to a higher voltage, and inverted to an alternating current (AC) voltage to normally AC-light a discharge lamp. However, at the time of starting up the discharge lamp, a high voltage pulse is produced by a starter transformer. The high voltage pulse generates electrical discharge between electrodes of the lamp due to dielectric breakdown thereby to form arc discharge so that stable lighting is ensured by the AC voltage thereafter.
The proposed apparatuses have various aspects to be improved further with respect to assemblability, mountability in a limited space, operability of electronic circuits and the like.
It is therefore an object of the present invention to provide a discharge lamp apparatus for vehicles which can be assembled and mounted in a limited space in a simplified process.
It is another object of the present invention to provide a discharge lamp apparatus for vehicles which operates properly under various conditions.
In one aspect of the present invention, an electronic circuit for a discharge lamp is integrated into a hybrid IC and disposed on the bottom of a metal case. Transformers, an inductor and a capacitor which are not integrated are disposed in a resin case. The resin case is contained in the metal case. In this instance, the transformers, the inductors and the capacitor are located outside the outer periphery of the IC so that the IC does not overlap on the transformer and other components.
In another aspect of the present invention, the transformer for a starter circuit has a secondary winding the inductance L2 of which is 2.5 mH or larger, and the capacitor of a DCxe2x80x94DC converter has a capacitance C2 which is 0.5 xcexcF or smaller. The switching frequency f of a MOS transistor of the DCxe2x80x94DC converter is selected so that L2xc3x97C1 is equal to or larger than 1xc3x9710xe2x88x921xc3x97fxe2x88x921.68.